206 1IOBPHOLOGY AXD EVOLUTION hand, bo it ij- evident that the Gorilla approaches Man nust doselv in the action of the interossei of the foot. MUSCLES of ~HE Diaphragm,^ — In the Chimpanzee, the comparatively small central tendon receives two slips from the back of the sternum, and fibres on each side from ribs 7-13. These slips interdigitate with the transversalis abdominis. The right crus arises from the second lumbar -vertebra and the left crus from the first. Additional slips also arise from the second lumbar transverse process and the first lumbar centrum. The lurnbo-cosLal arches varcnate ligaments) are as in Man. Sometimes the arches are not well defined. In the Gorilla the slips of origin of the muscular part do not interdigitate with the slips of the transversalis abdominis ; and the tendinous part of the muscle is large. The pericardium adheres to the upper surface : and the same structures pass through it as in Man. In the Orang the slips are strongly fused at their origin with the quadratus and psoas. ftuadratus Lumbortun. — In the Chimpanzee it arises from the posterior two-thirds of the inner lip of the iliac crest, where it is continuous with the iliaeus, and from all the lumbar transverse processes ; and it is inserted into the inner four-fifths of the last rib and the bodies of the last two dorsal vertebrae. In the Orang and Gorilla it is not fused with the iliaeus. External Oblique. — In the Chimpanzee it arises by digitations from the outer surfaces and lower borders of * Bertelli 1 13) has studied the morphology of the diaphragm.